The Ultimate Guide to Email Subject Lines

Don’t Call Me Cassandra

Researchers have found that it only takes seven seconds for others to form a first impression of you. And once a negative impression is formed, it takes eight positive encounters to offset the effects of the negative first impression.?

In light of this, it’s no surprise that subject lines are one of the most important parts of an effective email strategy.

Most of us have reacted negatively to emails with poorly written subject lines, and I am no exception. I recently got an email whose subject line read “Here’s My Vision For You, Cassandra Platt.” (!?) Since the sender got both my name and my gender wrong, I unsubscribed from the list.??

Writing engaging subject lines requires copywriting skills, but it also requires an understanding of the unique features of email as a marketing channel. Moreover, changes in technology impact how marketers should use subject lines in their campaigns.

In this newsletter, I’ll cover six subject line best practices that are essential for email marketers to know. I’ll explain how CoSchedule used these best practices to boost their open rates. I’ll also explain how open rates are not the only metrics that can be improved through subject lines.?

Let’s dive in!?

Six Important Subject Line Best Practices?

If you’re struggling to write engaging subject lines, using one or more of the best practices below can help you. The best practices are:?

1) Using first name personalization. Studies show that using the recipient’s first name in the subject line boosts open rates by an average of 26%. Email marketing tools like HubSpot and Mailchimp allow you to insert personalization tokens that dynamically populate with the recipient’s first name.?

2) Speaking in the second person. As much as possible, use “you” instead of “I,” “he,” “she,” or “we.” When you speak in the second person, you’re making it clear to your recipients that your campaign is about helping them and not about helping yourself.?

3) Asking questions. Questions spark curiosity. They also invite your recipients to enter into a dialogue with you, which makes them far more likely to respond. In one of my past email campaigns, I exceeded the open rate goal by 68% by adding questions to two of the subject lines.?

4) Including emojis. Emojis add an eye-catching visual element to your subject lines. Therefore, emojis tend to increase open rates. However, it’s important to note that closely related emojis can produce radically different results.

A study from Return Path analyzed subject lines for a New Year's email campaign. The study found that subject lines that used the champagne bottle emoji ?? led to a 22% open rate, whereas subject lines that used the clinking glasses emoji ?? only led to a 9% open rate.

5) Focusing on benefits rather than information. Email recipients always want to know how your message benefits them. Many email marketers fall into the trap of highlighting interesting product features without explaining why those features are beneficial to their audience.?

6) Avoiding words related to sales. In other marketing channels, words like “sale,” “discount,” and “free” can be some of the most powerful drivers of customer action. However, in email marketing, these words can do you more harm than good, especially when used in subject lines.?

Email service providers often flag emails that contain sales-related words as spam. Therefore, using sales-related words in your subject lines will hurt your sender reputation score and email deliverability.?

To learn more about spam trigger words, check out the video below.?

How CoSchedule Improved Its Subject Lines

CoSchedule is a North Dakota-based company that sells marketing calendar software to its clients. It sends a content marketing email newsletter to its subscribers on a weekly basis.?

CoSchedule decided to A/B test the subject line for each of its weekly newsletters over a one-month period. It got the following results:

The June 3 and June 10 newsletters generated the largest difference in open rates between the two variants. For both the June 3 and the June 10 newsletters, the winning variant made use of the best practices listed above.

For June 3, the subject line “17 Apps To Help You Make Ebooks” resulted in 13 more opens than “How We Grew Our Email List By 2,000+.”?

For June 10, the difference was even greater. “A No-Fail Method for Writing Blog Posts” led to 27 more opens than “50+ Places to Repurpose Your Content.”?

In both cases, the winning variant communicated benefits that were relevant to the customer. By contrast, the losing variant merely communicated information.?

In fact, “A No-Fail Method for Writing Blog Posts” had the highest open rate of any email sent in the month of June. This can be attributed to the fact that the benefit that CoSchedule highlighted - a guaranteed way to write successful blog posts - seemed nearly too good to be true. A nearly-too-good-to-be-true benefit will drive more opens than an ordinary benefit.?

Subject Lines Don’t Just Help With Opens

Although it’s important for email marketers to boost open rates, open rates have their limitations as metrics. Open rates reveal little about whether your marketing emails are motivating recipients to take positive action.?

For instance, your open rates will improve when recipients open your emails and mark them as spam. However, these interactions are harmful to your business rather than helpful.?

Thankfully, subject lines can be used to improve more than just open rates.?

In late 2020, email marketer Jeanne Jennings did a subject line A/B test on behalf of a B2B company. The company creates branded merchandise with a Christmas theme on behalf of its clients.?

The original subject line (i.e. the control) was “Holiday Gifts Under $10.” Jeanne tried rearranging the order of the words, as she thought that it might make the main benefit more visible. Therefore, she created a test subject line that read “Under $10 Holiday Gifts.”

The results of Jeanne’s A/B test were as follows:

In this test, the key metrics were the open rate, the click-through rate (CTR), the revenue-per-thousand-emails-sent (RPME), the conversion rate (CR from Sent), and the average order value (AOV).?

The open rate, click-through rate, and conversion rate were all lower in the test email than in the control. However, the RPME was much higher in the test email.?

The most important metric to Jeanne was the RPME. Therefore, Jeanne declared the test email to be the winner, even though it had a lower open rate.?

This example demonstrates that subject lines don’t have to result in large numbers of opens to be effective. A subject line that results in a small number of opens from heavily engaged subscribers can also be considered a success.?

Matthew’s Final Thoughts

Improving subject lines is the best thing that email marketers can do to improve open rates.?

However, subject lines can also be a powerful means of increasing revenue. Jeanne Jennings grew a client’s RPME by 63% by rearranging the order of the words in the subject line.?

Jeanne’s example also underscores the importance of context when implementing subject line best practices.?

Jeanne didn’t use tactics like first name personalization, emojis, or questions when creating her test subject line. To Jeanne, these tactics didn’t solve what she considered to be the main problem with the subject line. And that problem was the arrangement of the words.?

As it turned out, Jeanne’s hypothesis was correct, and the test subject line was a success.

As a result, email marketers should only use the subject line best practices that make sense in their particular situation.

Question of the month: What is the best email subject line that you've ever seen? Let me know in the comments!